checksum.h

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#ifdef __cplusplus
extern "C" {
#endif

#ifndef _CHECKSUM_H_
#define _CHECKSUM_H_

// Visual Studio versions before 2010 don't have stdint.h, so we just error out.
#if (defined _MSC_VER) && (_MSC_VER < 1600)
#error "The C-MAVLink implementation requires Visual Studio 2010 or greater"
#endif

#include <stdint.h>

#define X25_INIT_CRC 0xffff
#define X25_VALIDATE_CRC 0xf0b8

#ifndef HAVE_CRC_ACCUMULATE

static inline void crc_accumulate(uint8_t data, uint16_t *crcAccum)
{
        /*Accumulate one byte of data into the CRC*/
        uint8_t tmp;

        tmp = data ^ (uint8_t)(*crcAccum &0xff);
        tmp ^= (tmp<<4);
        *crcAccum = (*crcAccum>>8) ^ (tmp<<8) ^ (tmp <<3) ^ (tmp>>4);
}
#endif


static inline void crc_init(uint16_t* crcAccum)
{
        *crcAccum = X25_INIT_CRC;
}


static inline uint16_t crc_calculate(const uint8_t* pBuffer, uint16_t length)
{
        uint16_t crcTmp;
        crc_init(&crcTmp);
    while (length--) {
                crc_accumulate(*pBuffer++, &crcTmp);
        }
        return crcTmp;
}


static inline void crc_accumulate_buffer(uint16_t *crcAccum, const char *pBuffer, uint16_t length)
{
    const uint8_t *p = (const uint8_t *)pBuffer;
    while (length--) {
                crc_accumulate(*p++, crcAccum);
        }
}

#endif /* _CHECKSUM_H_ */

#ifdef __cplusplus
}
#endif